1. Field of the Invention
The present invention relates to actuators that convert a direction of action of driving force between a rotational direction and a linear direction and drive equipment.
2. Description of the Related Art
Conventionally, as actuators for driving various kinds of equipment in different fields such as, for example, in the field of aircrafts, actuators that convert a direction of action of driving force between a rotational direction and a linear direction and drive equipment are used.
U.S. Pat. No. 5,111,708 discloses an actuator that transmits, via a driving belt mechanism, rotational driving force generated by an electric motor, further converts this rotational driving force into linear driving force by a ball screw mechanism, and outputs the linear driving force. A literature titled “FLIGHT TEST EXPERIENCE WITH AN ELECTROMECHANICAL ACTUATOR ON THE F-18 SYSTEMS RESEARCH AIRCRAFT” published on the NASA website also discloses an actuator that converts rotational driving force generated by an electric motor into linear driving force by a ball screw mechanism, and outputs the linear driving force. Note that the above NASA literature is published on the Internet at the URL: http://www.nasa.gov/centers/dryden/pdf/88699main_H-2425.pdf.
Such an actuator as one disclosed in U.S. Pat. No. 5,111,708 or the above NASA literature is provided with a driving force conversion mechanism, such as a ball screw mechanism, for converting the direction of action of driving force between a rotational direction and a linear direction and transmitting the driving force. This driving force conversion mechanism, which is provided with a nut portion and a screw portion, converts the direction of action of driving force as a result of relative rotation of the nut portion and the screw portion.
In the above-mentioned driving force conversion mechanism, one of the nut portion and the screw portion rotates, and the other is linearly displaced. Therefore, a mechanism for restricting rotation of a linearly displaced element, which is one of one of the nut portion and the screw portion, is necessary. Note that the above NASA literature mentions that, to restrict the rotation of the screw portion that is linearly displaced in the ball screw mechanism, a rotation regulator to be built in or externally installed is separately needed.